Leaching and apparatus therefor



A3 SHEETS-SHEET I.

INVENTOR h #gina/:Aft .ATTORNEYS J. A. BAKER.

LEACHFNG AND APPARATUS THEREFOR. FILED Nov. 2.2. 1921.

Mar. 6, 1923.

Mar. 6, 1923.

J. Al BAKER.

LEACHING AND APPARATUS THEREFOR.

3 SHEETSA-SHEET 24 FILED NOV. 22. 192|.

INVENTOR www@ BY .y

WMWIWAMM/M ATTORNEYS MaI. 6, 1923. 1,447,637;

J. A. BAKER.

LEACHING AND APPARATUS THEREFOR.

FILED NOV. 22,1921- 3 SHEETS-SHEET 3.

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Ulli! ATToRNEY Patented 6, 1923.

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JOHN A. BAKER, F WESTPORT, CONNECTICUT.

`.LEACHING AND APPARATUS THEREFOR.

Application led November 22, 1921. Serial No. 516,949.

To all whom t may concern:

Be it known that I, JOHN A. BAKER, residing at lVestport, in the county of Faireld, State of Connecticut, have invented certain new and useful Improvements in Leaching and Apparatus Therefor; and I do hereby declare the following to be a full, clear and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In many metallurgical and chemical industries, the separation of a valuable element or elements from worthless or less valuable substances is accomplished by dissolving the former in a solvent in which the latter are insoluble. Such a process of leaching comprises three main steps, which are :4 first, pulverizing the material to be treated to a suitable fineness; second, agitating the pulverized material with the solvent for a suitable time; third, separating the dissolved element and its solvent from the insoluble residue. The present invention relates to the second and third of these steps.

lVhere it is necessary to carry the comminution, according to the first step, to eX- treme fineness, such as 150 or 200 mesh, the subsequent steps can be satisfactorily performed by several well known machinesthe paddle agitator, the Pachuca or the Dorr agitator. The material being so iinely ground remains in suspension long enough to permit such machines to do their work.

Where, however, such fine grinding is unnecessary and the leaching itself can be carried out with the material ground to pass only 60 or 80 mesh, or coarser, this coarse material settles so quickly thatthe abovementioned machines cannot well be used. The line at which these standard makes of agitators become inapplicable is not a hard and fast one, but varies with the character of the material and the4 permissible dilution of agitation. For example-crushed ore slime (speciic gravity of dry material 2.7) ground to 80 mesh (i. e. about 2% plus 80 mesh) at 2 to l dilution can be handled in any agitator of any of the above types. If, however, the dilution were increased to 4 to l, or the gravity increased to 5 or 6, great diiiiculty would be experienced, vand the continual mechanical troubles arising would cause opshort period in contact with water or similar solvent.

A machine of this type will do the ordinary work of leaching, but is open to certain objections. First of all it is inefficient. The cylinder'is never more than half full and therefore its capacity is not eiiiciently utilized. At the same time this unbalanced condition requires more power than would be necessary where the load is balanced. Another objection lies in the fact that the agitation must be carried out in contact with air, which in the case of oxidizable materials is a serious disadvantage. In some instances too the dissolving action is favorably influenced by the presence of certain gases, and it is dilicult or impossible to furnish such -an atmosphere when the agitation is performed in the common open-ended cylinder. Again, this type of agitator must operate under atmospheric pressure, whereas in some instances an increased pressure may be desirable. On the whole7 the common open-ended agitating and leaching cylinder operates not only inefliciently but in a limited field.

It is, therefore, the object of the present invention to devise an improved agitator which shall be free from these objectionable features, and by means of which more eilicient and varied methods of agitation and leaching may be carried out. This object has in general been attained by designing an agitator of the horizontal rotary cylinder type which is closed at both ends and fed and discharged through stuffing boxes. The material to be treated is fed from a source of supply above the level of the cylinder, and the treated material discharged into an open box, the overflow level of which may be varied from a pointnear the middle of the cylinder to a ploint above the top. By this arrangement t e level of the charge may be regulated and the pressure increased above atmospheric when desired. This discharge box drawings, which disclose a preferred embodi- 3 which support the cylinder in position for ment thereof, and in which Fig. 1 is a side elevation, partly in section, of a cylinder constructed in accordance with this invention; Fig. 2 is a transverse section of the cylinder taken along line 2 2 of Fig. 1; and Fig. 3 is a transverse section taken along line 3 3 of Fig. 1 and showing the construction of the discharge box.

The agitator as shown in these drawings comprises a horizontal rotary cylinder 1 equipped with the usual peripheral bands or tires' 2 designed to rest within flanged rollers rotation. The rotation is effected by means of power supplied to fast and loose pulleys 4 and thence transmitted through shaft 5, worm 6, worm wheel 7, pinion 8 and annular rack9 mounted upon the cylinder itself. The cylinder is equipped on its interior with a series of lifting bars 10 which engage the material during rotation of the cylinder, raise it and permit it to fall. The foregoing are features found in the common rotary open ended cylinder discussed above.

In accordance with the present invention the cylinder 1 is provided with closed ends, the end plates 12 and 13 lbeing riveted to the body of the cylinder and each provided with a stuiing box 14 and 15 respectively, concentric with the axis of the cylinder The material to be treated is introduced through a pipe 16 which enters stuffing box 14 and is connected to a feed hopper 17 located above the level of the cylinder. .The treated material is discharged through a pipe 18 which communicates with the interior of the cylinder through stuffing box 15. and leads to the discharge box 19. The discharge of the insoluble constituents is facilitated b'y means of two lifter arms 11 riveted to the inner face of endplate 13.

This discharge box 19 is provided with an inclined bottom 2O up which the in soluble residue discharged from the cylinder is carr'ied by means of a drag conveyor 22 and discharged into a trough 23. This conveyor 22 is mounted upon sprockets 24 and driven by power supplied through pulleys25. The overflow level of the box 19 is shown only slightly above the top of the cylinder. A series of discharge orifices 26. 27, 28 and 29 may, however, be provided so that the level of the material within the cylinder may be varied accordingly.- It is also possible to extend the side walls and the inclined bottom of the box 19, so that the pressure within the cylinder will be increased above atmospheric. By extending the inclined-bottom alone it would be possible to secure the discharge of a drierresidue than when this residue is discharged at a point practically on the level with the liquid constituent of the discharge as shown in Fig. 3.

Gas can be introduced to the interior of the cylinder through a pipe 31 which enters through stuffing box 15 and is connected to a source of supply through pipe 32. In order to ascertain the liquid level within the cylinder' when gas under pressure has been introduced, and the level in box 19 would not be indicative, a glass gauge tube 35 is provided, connected at one end with an extension of pipe 32 and to the other with the lower end of-box 19. The liquid in this tube stands at the same level as that within the cylinder.

I This pipe 31 when disconnected from the' gas supply pipe 32, as by a two-way cock 34, can be employed to release the air imprisoned within the cylinder when the latter is being filled. Another means for accomplishing this result comprises a series of spring pressed valves 35 arranged at intervals about the periphery of the cylinder and designed to be opened by means of a lfixed cam lever 36 positioned at the top ofA the cylinder, this lever contacting with one end of the valve and opening it as it passes the uppermost position. As the valve starts on its downward path it breaks contact with the cam 36 and is immediately closed, thus preventing the loss of any liquid. Only one suchvalve has been illustrated and may in some instances prove suflicient. i

The agitator is provided with pipes 37 and 38 which enter through stuffing boxes 14 and 15 respectively and through which high presure water maybe introduced to flush the cylinder. The cylinder is also provided with manholes 39 which may be employed when it is desired to obtain access to the interior of the cylinder for cleaning and other purposes.

The operation may be briefly reviewed as follows: The comminuted material and the solvent. usually water, is continuously fed from the hopper 17 through pipe 16 and stuffing box 15 to the.interior of the cylinder. If it is desired to operate with the cylinder filled, the overflow level of box 15 is fixed at 26 accordingly. The cylinder is rovtated and the material within the cylinder is thoroughly agitated and the soluble constituents leached out. Both soluble and insoluble constituents then pass off through pipe 18 to the discharge box 19, whence the dissolved material and its solvent are decanted at .26 and the insoluble residue dragged up the inclined bottom of the box vso by means of the drag conveyor 22 and discharged into the trough 23. If it is desired to agitate in the presence of a gas, such as fsuilfur dioxide, chlorine or bromine, such a gas is introduced through pipe 31. If it is desired that this gas be under pressure, or if it is desired that the agitation take place in the presence of air under pressure, it is only necessary to raise the sides and extend the bottom of the discharge box. The operation of the agitator is continuous and the desired conditions once established may be maintained indefinitely.

An agitator such as described above is free from the objections of the common openended cylinder. Instead of being only half full the agitator may be operated entirely full. The time of contact of the solvent and the solids is greatly increased, thus permitting the same work to be done by a much smaller cylinder, or in largely increasing the capacity'of a cylinder of the same size. Another advantage is that less power is required because the cylinder being full is nea-rer balanced. This drop in power for a single cylinder is estimated at 15%, and since the cylinder contains double the amount of an open trunnion cylinder, the saving in power per ton of material treated is 30%. By means of such a cylinder agita tion can be effected Without contact with air. With oxidizable materials, such as sodium sulfide, this is an advantage of prime importance. Another advantage not evident at first glance is that the character of the displacement of the fiuid contents has altered. In a three phase system, such as in .the ordinary open trunnion cylinder, the surface of contact between liquid and gas tends to become the line of least resistance and hence of quickest flow. This promotes short circuiting. In the full cylinder, on the other hand, provided the incoming'central current is properly broken up, the flow is distributed through the entire cross section of the cylinder. It is also possible'by means of this agitator to operate in the presence of any desired ges and to Vary the pressure when this becomes necessary.

Although one preferred embodiment of the invention has been shown and described, it is clear that the invention is not limited to the details of construction shown herein. For example, one specific type of drag chain has been shown :for removing the insoluble residue from the discharge box. Many other means, of course, might be employed to ac complish this result. The scope of the invention is defined in the appended claims.

I claim:

l. The improvement in the method of agi tatingapmixture containing solid material and an-liquid hy rotating a cylindrical vessel containing the mixture. which comprises feeding the mixture to be agitated at one end of the vessel anddischarging the agi tated mixture fromthe other end of the vessel in a substantially continuous manner and maintaining the vessel more than half full of liquid during its rotation and during the feeding and discharging thereof as aforesaid.

2. The improvement in the method of agitating a mixture containing a liquid and finely divided solid material so ground that a substantial percent thereof is plus 80 mesh by rotating a cylindrical vessel containing the mixture, which comprises feeding the mixture to be agitated at one end of the vessel and discharging the agitated mixture from the other end of the vessel in a substantially continuous manner, and maintain- `and controlling said feeding and discharging opera-tions so that the vessel is maintained more than half full of liquid during its rotation and during the feeding and dis'. charging thereof as aforesaid.

4. The improvement in the method of agitating a mixture containing solid material and a liquid by rotating a cylindrica'l vessel containing the mixture, which comprisesv maintaining the vessel more than half full of the mixture at a pressure above that of the atmosphere, and feeding the mixture to be agitated at one end of the vessel and discharging the agitated mixture from the other end of the vessel during the rotation of the vessel and while the vessel is maintained more than half full of the mixture undergoing agitatio-n.

5. The improvement in the method of agitating a mixture containing a liquid and finely divided solid material so ground that a substantial percent thereof is plus 8O mesh, by rotating a cylindrical vessel c0ntaining the mixture, which comprises maintaining the vessel more than half full of the mixture at a pressure above that of the atmosphere, and feeding the mixture to be agitated at one end of the vessel and discharging the agitated mixture from the other end of the vessel during the rotation of the vessel and while the vessel is maintained more than half full of the mixture undergoing agitation.

6. An apparatus for agitating a mixture containing finely Vdivided solid materia-l and a liquid, comprising a cylindrical vessel, means for rotating said vessel, means for feeding the mixture to be agitated at one end of the vessel and means for controlling the discharge of agitated material from the Other end of the vessel so as to maintain the vessel more than half full of the mixture undergoing agitation therein.

7. An apparatus for agitating a mixture containing finely divided solid material and a liquid, comprising a cylindrical vessel, means for continuously feeding the mixture to be agitated tothe vessel, means for c0ntinuously discharging the agitated mixture from the vessel, means for controlling the discharge of agitated material from the vessel so as to maintain the vessel more than half full of the mixture undergoing agitation therein, and means for permitting the escape of gas from the vessel during the rotation thereof.

8. An apparatus for agitating a mixture containing finely divided solid material and a liquid, comprising a c-ylindfrical 'vesseil provided with stuffing boxes at each end thereof, means for feeding the mixture to be agitated into the vessel through the stuffing box at one end thereof, means permit-y ting the discharge of the agitated material from the vessel through the stuliing box at the other end thereof, and a Well communieating with said discharging means and having a liquid overflow at such a height as to maintain the vessel during its rotationmore than half full of the mixture undergoing agitation.

9. An apparatus for agitating a mixture containing finely divided solid material and a liquid, comprising a rotatably mounted cylindrical vessel, a feed pipe centrally positioned at one end of said vessel and communicating with the interior thereof, a discharge pipe centrally positioned at the other end of said vessel and communicatrotation more than half full of the mixture undergoing agitation therein.

10. An apparatus for agitating a mixture containing finely divided solid materia-hand a liquid, comprising a cylindrical vessel. means for rotating said vessel, means for feeding the material to be agitated at one end of the vessel, means for controlling the discharge of agitated material from the other end of the vessel so as to maintain the vessel more than half full of the mixture undergoing agitation therein, and means for introducing a gas tothe interior of the vessel. i

ll. An apparatus for agitating a mixture containing finely divided solid material and a liquid, comprising a cylindrical Vessel, means for rotating said vessel, means for feeding the mixture to be agitated to the vessel, a discharge box into which the treated'material is dischargedv` and a plurality of overflow orifices in said discharge box by means of which the level of the material in the vessel can be regulated.

12. An apparatus for leaching soluble material from finely divided solid material. comprising a cylindrical vessel, means for rotating said vessel, means for feeding the solid material and a solvent to the vessel. a discharge box into which the treated inaterial is discharged. means in said discharge box for removing the insoluble residue, and means for decanting the solution of leached material from the discharge box so as lto regulate the level of liquid in the vessel.

In testimony whereof I aiiix my signature.

JOHN A. BAKER. 

